1. Field of the Invention
The present invention relates to a threaded closure for a large pipe or vessel and more particularly a horizontal hinged closure used for scraper traps, large O.C. filter units, launchers, receivers, and other similar installations.
2. Description of the Related Art
Referring now to FIG. 4, there is illustrated a typical prior art female threaded closure that employs a center mounted bearing located at the rear of the threaded head. The center mounted bearing serves as a means of suspending the threaded head whenever it is removed from the male threaded structure to which it attaches. Suspending the threaded closure is necessary to allow the threaded closure to be attached and removed from a male threaded structure since these closures can weigh several hundred or several thousand pounds and are generally too heavy to be handled without the aid of some type of suspending device.
One of the problems with prior art threaded closures of this type is that the center mounting arrangement causes the center of gravity to be located rearward on the head so that when the head is disengaged from the male threaded structure, the upper portion of the head tends to tilt forward and the lower portion of the head tends to tilt rearward. This tilted orientation of the head makes it difficult and time consuming to again raise and turn the head to the proper orientation to thread it back onto the male threaded structure.
The present invention addresses this problem by eliminating the center mounting arrangement and instead employing a large diameter track ring that attaches directly to the rear of the threaded head. The present invention also employs a bearing ring with cam followers that engage the track ring to allow the threaded head to be rotated relative to the male threaded structure. By rotating the threaded head in a counterclockwise manner, this loosens and removes the threaded head from the male threaded structure. Alternately, by turning the threaded head in a clockwise manner, this tightens and reattaches the threaded head to the male threaded structure.
As with prior art threaded heads, the bearing ring of the present invention is attached to a hinge arm that allows the threaded head to be moved linearly away from the male threaded structure once the threaded head is removed from the male threaded structure and also allows the threaded head to be rotated about a vertical axis once it is moved away from the male threaded head.
Because of the direct attachment of the large diameter track ring to the rear of the threaded head of the present invention, the center of gravity is moved forward of where it is located on the prior art female threaded closure of FIG. 4. Because of this shift in the center of gravity on the present invention, the threaded head does not tilt to any great extent when it is removed from the male threaded structure, and this makes aligning and reattaching the threaded head to the male threaded structure much easier and faster. In fact, employing the present invention, a single man can easily align and reattach a thousand pound threaded head to a male threaded structure in just a matter of minutes. To accomplish the same alignment and reattachment with a prior art threaded head of similar weight would normally take a couple of people anywhere from 30 minutes to an hour.